title: Erythropoietin prevents hypoxia-induced GATA-4 ubiquitination via phosphorylation of serine 105 of GATA-4.
abstract: Erythropoietin (EPO), an essential hormone for erythropoiesis, can provide protection against myocardial ischemia/reperfusion (I/R) injury and hypoxic apoptosis. GATA-4 is a zinc finger transcription factor, and its activation and post-translational modification are essential components in the transcriptional response to hypoxia. GATA-4 has also been reported to play a role in the cellular mechanisms of EPO-induced myocardial protection against I/R injury. In this study, we aimed to investigate the influence of EPO on GATA-4 protein stability and post-translational modification under hypoxic conditions without reperfusion. EPO induced cell viability under long-term hypoxia. EPO significantly increased phosphorylation of GATA-4 via the extracellular signal-regulated kinase (ERK) signaling pathway and reduced hypoxia-induced GATA-4 ubiquitination, which enhanced GATA-4 stability under hypoxia. ERK activation by over-expression of constitutively active mitogen-activated protein kinase 1 (MEK1) strongly increased GATA-4 phosphorylation and its protein levels and decreased GATA-4 ubiquitination under hypoxia. Despite ERK activation, GATA-4 ubiquitination was not affected under hypoxia in a GATA-4-S105A mutant. Under hypoxic condition without reperfusion, EPO-induced ERK activation was associated with post-translational modification of GATA-4, mediated by enhancement of phosphorylation of GATA-4 at Ser-105. Subsequent attenuation of GATA-4 ubiquitination led to increases in GATA-4 protein stability, which resulted in increased cell viability under hypoxia.
authors.affiliation: Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul 120–752, Republic of Korea.
authors.forename: Ji Hae
authors.initials: JH
authors.lastname: Jun
authors.forename: Eun Jung
authors.initials: EJ
authors.lastname: Shin
authors.forename: Ji Ho
authors.initials: JH
authors.lastname: Kim
authors.forename: Si Oh
authors.initials: SO
authors.lastname: Kim
authors.forename: Jae-Kwang
authors.initials: JK
authors.lastname: Shim
authors.forename: Young-Lan
authors.initials: YL
authors.lastname: Kwak
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002316:Cardiotonic Agents / Q000494:pharmacology*; D015687:Cell Hypoxia / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004921:Erythropoietin / Q000494:pharmacology*; D050991:GATA4 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D047468:Immunoprecipitation; D016297:Mutagenesis, Site-Directed; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism; D010766:Phosphorylation; D061251:Primary Cell Culture; D055550:Protein Stability; D051381:Rats; D017207:Rats, Sprague-Dawley; D012694:Serine / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: D002316:Cardiotonic Agents; D050991:GATA4 Transcription Factor; D004921:Erythropoietin; D012694:Serine